A threshold is added to recognize an input pattern that has too few similarities to be one of the memory patterns. A real-time pattern recognition system based on the improved model is given. The unipolar optical pattern recognition system has all the characteristics of a fully bipolar winner-take-all model and has illumination invariance. A liquid-crystal spatial light modulator is used as a real-time input device, and a mask and a lens array perform the threshold and weighted sums of the input pattern. Some experimental results are also shown.